Vaccine may offer producers alternative to castrating calves

However, an alternative to traditional methods could be a vaccine that reduces testosterone in bulls approaching puberty.

Researcher Sonia Marti Rodriguez compared the effects of the vaccine with banding young bulls at Agriculture Canada’s Lethbridge research centre.

The vaccine was given twice every three to four months to be effective, she said at a June 19-20 beef cattle conference organized by the University of Calgary’s veterinary faculty.

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The study banded the testicles of another group of bulls and monitored their behaviour, pain responses and body and testicle temperatures.

The testicles sloughed off by 42 days as the band tightened. The bulls showed pain during the entire period as indicated with rising cortisol concentrations in saliva and tail flicking.

The vaccinated calves had greater average daily gains by Day 56 than the band castrated calves, although feed intake slowed down during the first two to three days after vaccination.

She said there was some fever after the injection. Some studies have found inflammation in the neck area where the vaccine was injected, but she did not notice swelling.

The testicles of vaccinated cattle were 65 percent smaller than intact bulls by slaughter time. There was no difference in carcass grade.

The product is Bopriva, manufactured by Zoetis. It has been approved in New Zealand, Australia, Brazil, Argentina, Mexico, Peru, Turkey and parts of Central America. It is not approved in Canada and the United States, but it is being tested.

The vaccine inhibits the growth hormone gonadotropin, which reduces testosterone levels for three to four months.

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This results in decreased sexual and aggressive behaviour and easier management of bulls.

The vaccine should be used for animals entering puberty. There has only been one study with younger calves.

Zoetis’s website advises it should not be used on breeding stock, and pregnant women should not give the injections.